1. Field of the Invention
The present invention relates to agricultural harvesters such as combines, and, more particularly, to sieve assemblies incorporated in the harvester crop processing section having the capability for side to side shaking motion.
2. Description of the Related Art
An agricultural harvester known as a “combine” is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning. A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves, and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves and is transported to a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. The cleaning system includes a cleaning fan which blows air through oscillating sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material such as straw from the threshing section proceeds through a straw chopper and out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
More particularly, a rotary threshing or separating system includes one or more rotors which can extend axially (front to rear) or transversely within the body of the combine, and which are partially or fully surrounded by a perforated concave. The crop material is threshed and separated by the rotation of the rotor within the concave. Coarser non-grain crop material such as stalks and leaves are transported to the rear of the combine and discharged back to the field. The separated grain, together with some finer non-grain crop material such as chaff, dust, straw, and other crop residue are discharged through the concaves and fall onto the grain pan where they are transported to the cleaning system. Alternatively, the grain and finer non-grain crop material may also fall directly onto the cleaning system itself.
The cleaning system further separates the grain from non-grain crop material, and typically includes a fan directing an air flow stream upwardly and rearwardly through vertically arranged sieves which oscillate in a fore and aft manner. The air flow stream lifts and carries the lighter non-grain crop material towards the rear end of the combine for discharge to the field. Clean grain, being heavier, and larger pieces of non-grain crop material, which are not carried away by the air flow stream, fall onto a surface of an upper sieve (also known as a chaffer sieve or sieve assembly) where some or all of the clean grain passes through to a lower sieve (also known as a cleaning sieve). Grain and non-grain crop material remaining on the upper and lower sieves are physically separated by the reciprocating action of the sieves as the material moves rearwardly. Any grain and/or non-grain crop material remaining on the top surface of the upper sieve or sieve assembly are discharged at the rear of the combine. Grain falling through the lower sieve lands on a bottom pan of the cleaning system, where it is conveyed forwardly toward a clean grain auger. The clean grain auger is positioned below the lower sieve, and receives clean grain from each sieve and from the bottom pan of the cleaning system. The clean grain auger then augers the clean grain laterally sideways to a clean grain elevator, which in turn conveys the clean grain to a grain tank onboard the combine.
The upper sieve or sieve assembly is driven in fore and aft movement to move the harvested crop material in an aft direction and at the same time to separate the remaining grain or crop from the non-crop material. When the agricultural harvester is on the side of a slope, side to side movement of the sieve assembly is required so as to prevent downhill pooling of the material and resultant reduction in capacity and/or efficiency by evenly distributing the material across the sieve assembly. The side to side movement is used generally selectively so that the continuous primary movement is fore and aft. Further, the side to side movement is often adjustable in preset increments. For example, 3 millimeters of side to side movement per degree of lateral side slope inclination may be chosen as a recommended setting for small seeds. 2.5 millimeters per degree may be recommended for medium sized seeds. 2 millimeters per degree may be recommended for large sized seeds. These settings may be based on an assumption that the agricultural harvester will be operating at its maximum capacity for the crop being processed, limited by the power limit of the agricultural harvester. Alternately, the same settings may be used for all crops, irrespective of seed size.
However, in practice, it is often not feasible or necessary to continuously utilize these amounts of side to side movement of the sieve assembly, not only due to variations in the amount of side slope being experienced by the agricultural harvester, but also because the amount of crop being processed at a given moment may not require the maximum capacity of the agricultural harvester. Specifically, the amount of crop being processed may change as the agricultural harvester proceeds, as it passes through areas of greater or lesser yields.
In other words, a certain amount of side to side movement of the sieve assembly is necessary to prevent downhill pooling of the crop material and resultant reduction in capacity and/or efficiency at a given amount of side slope when the agricultural harvester is operating at its maximum capacity for the crop being processed. However, when the agricultural harvester is not in fact operating at its maximum capacity, continuous use of the amount of side to side movement necessary at maximum capacity results in unnecessary damage to components, including wear and tear on the sieve assembly and on the side shaker mechanism that is used to cause the side to side movement.
Accordingly, what is needed in the art is a system or method that automatically adjusts the amount of side to side shaking motion of the sieve assembly according to the amount of crop being processed at a given moment under a given amount of side slope.